1. Field of the Invention
The present application relates generally to oil field devices and, more particularly, to a plunger assembly with protective coatings and pads to reduce wear.
2. Description of Related Art
The oil and gas industry has been drilling holes and removing natural crude oil for decades. Plungers are downhole tools used by operators to remove contaminants from productive natural gas wells. A plunger acts as an artificial lift. In operation the plunger passes down through the surface tubing of the well until it reaches a contact point, at which point potential energy of the plunger falling in the well acts to partially restrict the flow of working fluid through the plunger. Pressure beneath the plunger builds and raises the plunger to the surface, thereby pushing out the liquids and contaminants above the plunger.
A number of disadvantages exist with current plungers. Conventional plungers direct the flow of working fluid around the plunger and between a portion of the plunger and the tubing of the well bore. The working fluid contains small debris which can quickly wear down the surfaces of the plunger tool as it repeatedly passes through the tubing. The main body of the plunger and the dart are most susceptible. A method of protecting the body of the plunger from corrosive/abrasive wear is needed.
Another disadvantage is that the body of conventional plunger assemblies are composed of a plurality of parts that are coupled together. One reason for this is that a user desires to maintain access to the dart in case of wear or damage. The ability to dismantle a plunger assembly allows the user to remove and replace the dart. However, connections in the body often succumb to the stresses experienced within the well bore and provide a weak link. A single uniform body is needed that can allow for the removal and replacement of the dart.
Furthermore, stresses experienced by the plunger assembly at impact at the bottom of the well bore can be extreme in nature. Typically the dart is pushed to a lower position relative to the body (i.e. extending below the body) when passing down the surface tubing. At impact with a stop at the bottom of the surface tubing, the dart is abruptly pressed upward against the body. The dart experiences some of the stresses but the body of the plunger, and particularly the lower tip of the body absorbs a majority of the impact. These forces are primarily transferred to the main body through the tip of the lower body. In an attempt to avoid damage, the lower end of the body is often thickened. Despite these efforts, if the plunger is not centered in the surface tubing or aligned correctly with the stop then the lower end of the body can be damaged (i.e. bent) upon impact. An improved method of transferring the forces to the main body is desired so as to avoid damage to the lower end of the body.
Although great strides have been made, considerable shortcomings remain.
While the assembly and method of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the application to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process of the present application as defined by the appended claims.